1. Field
One embodiment of the present invention relates to a disk drive, and in particular, to a servo write technique for spiral servo patterns.
2. Description of the Related Art
In general, in disk drives typified by hard disk drives, servo patterns (servo data) used for head positioning control are recorded on a disk medium that is a data recording medium. The disk drive uses the servo patterns read by the head to controllably place the head at a target position (target track) on the disk medium.
The servo patterns recorded on the disk medium have a plurality of servo sectors normally arranged circumferentially at a fixed interval so as to constitute concentric servo tracks. The disk drive positions the head on the basis of the servo patterns and uses the head to record user data on the disk medium to construct concentric data tracks.
The servo patterns are recorded on the disk medium by a servo write Block included in a disk drive manufacturing process. A proposal has been made of a method of recording a plurality of spiral servo patterns (hereinafter referred to as spiral servo patterns) constituting base patterns (seed patterns) on the disk medium during the servo write Block (see, for example, U.S. Pat. No. 5,668,679).
In the servo write Block in accordance with the proposed method, a plurality of spiral servo patterns (multi-spiral servo patterns) are recorded, by, for example, a dedicated servo track writer (STW), on the disk medium not incorporated yet in a disk drive to be shipped as a product. Alternatively, a head in the drive itself records the spiral servo patterns.
The disk medium is subsequently incorporated into the disk drive, which performs a servo self-write method to write concentric servo patterns (hereinafter referred to as specified servo patterns for convenience) used for the product to the disk medium. The specified servo patterns constitute the concentric servo tracks.
When the spiral servo patterns are written to the disk medium, a clock track is written to the disk medium to determine a timing at which an operation of writing the spiral servo patterns is started. The clock track is a concentric track pattern written to the boundary of a data storage region which is located on the innermost periphery of the disk medium, by pressing a head of the servo track writer against an inner peripheral stopper.
The head is separated into a read head made of a GMR element and a write head, both of which are mounted on a slider. This results in a deviation called an offset between a position where the read head reads data from the disk medium and a position where the write head writes data to the disk medium.
When an operation of writing the spiral servo patterns to the disk medium is started, the read head reads the clock track to generate a write timing for the spiral servo patterns. In this case, the offset makes it difficult to allow the read head to read the clock track from the position where the write head has written the clock track.
Thus, before the operation of writing the spiral servo patterns to the disk medium, a process needs to be executed which searches the disk medium for a position where the read head can read all of the clock track. The searching process needs to be executed every time one multi-spiral servo pattern is written to the disk medium. Therefore, the searching process requires a relatively long time, reducing the efficiency of the process of writing the spiral servo patterns to the disk medium.